Method of separating fine granular materials according to specific gravity



Oct. 10, 1950 E. M. BAROODY 2,525,390

METHOD OF SEPARATING FINE cmwum MATERIALS ACCORDING TO srscmc GRAVITY Filed Dec. 26, 1946 EUGENE M. BAEooDY,

Patented Oct. 10, I950 METHOD OF SEPARATING FINE GRANULAR MATERIALS ACCORDING TO SPECIFIC GRAVITY Eugene M. Baroody, Columbus, Ohio, assignor to The Jeifrey Manufacturing Company, a corporation of Ohio Application December 26, 1946, Serial No. 718,422

1 I This invention relates to an improved method of separating fine. granular materials according to specific gravities.

-An object of the invention is to provide'an lation to the characteristic frequency of the par- I ticles of one of the minerals being separated.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings,

Fig. 1 is a front elevational view of one form of apparatus for carrying out my' invention; and

Fig. 2 is a side view of said apparatus, with parts shown in section.

The Jig or classifier disclosed for carrying out my invention is disclosed in full detail in the application of Frank P. Smith, Serial No. 668,845, filed May 10, 1946. Briefly described, it includes a deck, container or tank In which provides a compartment or receptacle for receiving granular mineral, such as fine iron ore, which is to be separated into two groups of particles according to specific gravity. The apparatus is designed particularly for treating relatively small size particles.

The fine iron ore to be separated from its gangue, particularly silicon, is fed to the deck ID with an appreciable quantity of water'so as to provide an ore pulp which will have a normal level in the container or compartment III, as indicated at H in Fig. 2 of the drawings. The pulp will flow freely down an inclined feed chute l2 into the main part of the compartment ill. The container I0 is provided with a false bottom IS in the form of a screen which is held down by appropriate hold-down means It in cooperation with a supporting egg-crate partition which helps distribute the water through the perforations in the false bottom screen l3. In one successful form of the device the screen or false bottom l3was a multipore rubber screen. It is preferably a very fine mesh screen. I have successfully used screens [3 with a mesh varying from 65 to H5. If desired, a shot bed may also be used on screen l3, or as a substitute there- 4 Claims. (Cl. 209-422) 2 a hutch compartment l6 which is formed as a part of the container l0 and below the screen I 3. Hutch compartment I6 is provided with a pluralityof longitudinally extending water feed pipesll by which a relatively small amount of,

water is introduced into the various cells of the egg-crate partition Ill, which water flows upwardly through the screen plate It into the pulp compartment Ill. The hutch compartment l8 nd through it the container I0 is supported on a stationary frame l8.

The central bottom portion of the hutch compartment l8 is in the form of a diaphragm ll which is attached to theadjacent bottom portion by means of a rubber ring 20 which provides a fluid-tight bottom for said hutch compartment [6 but which allows reciprocation of the diaphragm l9 rectilinearly upwardly and downwardly. This rectilinear vibratory motion is delivered to the diaphragm 19' by a vibratory electro-magnetic motor 2|, the armature head 22 of which is rigidly attached to said diaphragm IS. The motor 2| preferably follows the, structure shown in the patent to James A. Flint, No. 2,094,698, dated October 5, 1937, for a Device for Packing Materials.

Adjacent the discharge side of the container III, which is to the right, as viewed in Fig. 2, there is a weir 23 over which the gangue or refuse fiows, being guided'therefrom by gangue discharge chute 24. Preferably located alongthe longitudinal center of and within the container or compartment 10 and provided by a substantially U-shaped upstanding wall, plate or partition 25 is a concentrate or high gravity material cell or compartment 26. As is clearly illustrated, particularly in Fig. 2 of the drawings, the plate 25 extends both above and below the normal pulp level II, and the bottom edge thereof is close to but slightly above the false bottom or screen It.

As hereinafter described more completely, the bottom edge of the plate 25 also extends slightly below the level of the bed of concentrates or high gravity material which forms in the bottom of the compartment I!) under the classifying or jigging action which takes place. The depth of a typical concentrates bed is illustrated at 2? in Fig. 2 of the drawings. A weir "having preferably the same height as the weir 23 is provided for the concentrates cell or compartment 26 and the concentrates which flow over the weir 28 are received by a trough 29.

It is evident from the above description that the cell 26 formed by the plate or partition 25 provides what is, in efiect, a dam and seal concentrates draw. It has been found, however, that the dam and seal type of concentrates draw may have its efiiciency very vastly improved so as to prevent all land-sliding, which such draws tend to produce, by providing a skimmer means, or other functionally equivalent mechanism, for removing concentrates from the concentrates cell or compartment 26, In the illustrated form of mechanism for thus removing concentrates and causing them to flow over the weir 28 a I skimming mechanism is provided in the form of a skimming paddle wheel 30 which is preferably continuously operating at a variable speed, as described more completely in the above identified Smith application, the wheel 30 being preferably rotated in a counter-clockwise direction, as viewed in Fig. 2 of the drawings, so as to skim the top of the concentrates from the cell 26 and to cause it to flow over the weir 28 into the trough 29.

Mechanism for controlling the rate of withdrawal of concentrates from the cell 26 is described completely in said Smith application and will not be here repeated.

A study of the operation of the high frequency jig above described reveals that improved separation of fine granular materials may be effected if certain conditions of operation are realized. Without attempting to explain the theory or reason which produces these improved results, it may be stated that the small or fine particles suspended in a fluid or liquid and subjected to a constant velocity upwardly flowing water upon which there is superposed a harmonic vibration have, what I call, a characteristic frequency, designated in. The characteristic frequency of particles in water may be calculated from the equation in is equal to in which jn=characteristic frequency v=kinematic viscosity of liquid (coefflcient of viscosity divided by density);

r=radius of material particles in centimeters;

d=ratio of particle density to fluid density.

From this equation a table may be made which shows the characteristic frequencies of various size particles, the size being given in both mesh and radius in centimeters where the particles are in water and the specific gravity is 3 in one case and 5. in the other.

Characteristic frequencies (f) [Particles water-.1

Sim Specific Gravity Mesh Radius, Cm. d=3 d=5 20 0. 04 1. 51sec 0. 9/sec. 100 0.)? 50 30 150 0.005 100 60 M 0.004 150 90 400 0.002 000 360 .01 and calculated for this value 1; will become .01 divided by 1 or .01.

To give an example of the calculation of In in the equation for a particle of 100 mesh size or .007 centimeters radius and a specific gravity of 5, we have 4.r .oo7)= 5 To effectuate a very efficient separation of minerals of a single size in accordance with my improved method, the operating frequency of the jig (I) should be approximately equal to or greater than (in) the characteristic frequency of the smallest particles. Under these conditions there will be a very efiicient gravity separation, with the high gravity particles forming a layer of concentrates, as seen at 21, and the gangue flowing over the weir 23.

In many practical installations it will be undesirable to treat only a single size range and in such circumstances generally three mesh sizes 29.3 approx.

of the same minerals may be treated and obtain practical successful results. Under these circumstances the natural frequency of vibration employed 'is to be selected near the characteristic frequency of the smallest particle being separated. Furthermore, it is found very desirable that the stroke be a few times larger than the diameter of the largest particles being separated, for example, from 2 to 5 times, which is to be understood as the meaning of the expression few times as used in the claims. This is because experience has shown that some vibration is essential to effectuate the improved classifyingaction while requiring a much smaller amount of upwardly flowing current than normally employed in an upward current classifier, but if the amplitude becomes too great the unit will tend to act as a barrel packer and pack all of the granular material solid which, of course,

'is disastrous to a classifying action.

In this particular it may be mentioned that while one of the effects of the vibration is to impartmobility to the bed, this is by no means the principal effect of it, because mobilit might be imparted by horizontal vibration as against a vertical vibration, However, the improved classifying action derived by tuning the operating frequency (f) to the characteristic frequency (in) of the smallest particles is only realized to its greatest extent where there is vertical rectilinear vibratory movement or at least vibratory movement having a vertical component. In other words, there is a definite supporting action on the minerals derived from the vertical vibration. Furthermore; vibration alone will not support the particles and consequently some upwardly flowing currentvof fluid is found necessary, though with my improved method the amount of upwardly flowing current is greatly reduced, as compared with that of an upward current classifier.

Where, in the claims, reference is made to fine material, or the equivalent, without specifically limiting the size or size range, it is to be understood that the material is between 50 mesh and 400 mesh.

It may further be mentioned that in the carrying out of the method by the disclosed apparatus the vibration of the diaphragm I9 is reproduced in the column of water supported by it so that the column of water moves upwardly and downwardly with the diaphragm.

Obviously those skilled in the art may make various changes in the details and arrangement auaaaeo ment of my invention, what I desire to secure by Letters Patent of the United States is:

1. The method of separating fine iron ore from gangue including subjecting a bed of said materials to the combined influence of upwardly flowin fluid current and substantially rectilinear vertical vibration in which the frequency of the vibration is approximately equal to and greater than the characteristic frequency of the smallest particles being separated and in which the amplitude of said vibration isa few times larger than the particle sizes, the characteristic frequency (in) substantially satisfying the equation 2. The method of separating fine iron ore from gangue including subjecting a bed of said materials to the combined influence of upwardly flowing fluid current and substantially rectilinear vertical vibration in which the frequency of the vibration is approximately equal to the char- 3. The method of separating flne iron ore from gangue including subjecting a bed of said materials to the combined influence of upwardly flowing fluid current and substantially rectilinear vertical vibration in which the frequency of the vibration is approximately equal to the characteristic frequency of the smallest particles being separated, the characteristic frequency (Io) substantially satisfying the equation I 9v 111 11 a I 4. The method of separating fine ironore from gangue including subjecting a bed of said materials to the combined influence of upwardly flowing fluid current and substantially rectilinear vertical vibration in which the frequency of the vibration is approximately equal to the characteristic frequency of the smallest particles be- 4 ing separated.

EUGENE M. BABPODY.

REFERENCES CITED The followingreferences ,are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 1,910,386 Garrett May 23, 1933 2,122,028 Daman June 28, 1938 2,333,347 Trostler Nov. 2, 1943 k FOREIGN PATENTS Number Country Date D. 643,486 France May 16, 1928 660,283 Germany May 20, 1938 17,256 Great Britain of 1906 148,168 Great Britain May 10, 1921 OTHER. REFERENCES Gaudin: Principles of Mineral Dressing. pages Taylor: The Separation of Metallic Ores by Jigging, Transactions Institution of Mining and Metallur y. v01. 18, 1908-9, pages 2 to 24.inclusive. 

